1. Technical Field
The present invention relates to a biometric authentication device, which performs biometric authentication by capturing the shadow of a vein.
2. Description of the Related Art
Generally, biometric recognition is a method of verifying the identity of an individual using his or her peculiar physical characteristics or habits. Biometric recognition as such has been applied to and used in various fields, for example, the field of security.
That is, biometric recognition has been widely used to perform personal identification in a variety of environments ranging from a physical environment related to identifying an individual to manage admissions or use cash dispensers, to a cyber environment related to identifying an individual for electronic commerce based on the Internet or telebanking.
Personal identification based on such biometric recognition has various advantages compared to identification based on a password or an ID card, the most remarkable of which being that biometric recognition is used for authentication accompanied by the presence of an individual.
There is a concern that, in the case of identification based on a password or an ID card, these may be lent out or lost and be then misappropriated. However, identification based on biometric recognition is advantageous in that an individual is authenticated only when the individual is present, thus improving the reliability of verifying the identities of individuals.
Furthermore, identification based on biometric recognition is superior in terms of the convenience to identification based on a password or an ID card. The reason for this is that an individual does not need to be in personal possession of the ID card nor have to memorize a password.
Meanwhile, methods of biometric recognition are classified into a method using physical characteristics, such as the face, the iris, the retina, voice, fingerprints and veins, and a method using physical habits such as a signature and a writing style.
Among the methods, vein recognition is a biometric recognition technique which uses the patterns of veins inside a human body and is devised in light of the fact that the pattern of veins is different between persons.
Vein authentication based on such vein recognition is implemented using a principle in which infrared light having a wavelength of 700 to 1000 nm can easily pass through a large part of body tissue, but can be easily absorbed by the hemoglobin of red blood cells flowing in the veins.
That is, when an image of a finger is captured using an infrared camera module and is then observed, veins appear as a shadow. Vein authentication is a scheme for identifying each individual using the characteristics of veins, and enables identification regardless of the states of the surface of the finger, such as the state of dryness, thus decreasing the erroneous recognition rate compared to authentication using fingerprints, and making it impossible to forge venous images unlike fingerprints.
However, such a conventional biometric authentication device is accompanied by a large cost burden because an expensive infrared camera module must be used to capture an image of the finger.
In the case of a typical camera module, a lens-shaped infrared cut-off filter or an infrared cut-off film is fundamentally included in an optical system. Since both a Complementary Metal-Oxide-Semiconductor (CMOS) sensor and a Charge Coupled Device (CCD) sensor can detect infrared light, infrared light in natural acts as noise when an image is captured.
Therefore, a typical camera module includes as a basic part thereof an infrared cut-off filter. In a typical camera module for mobile devices, the surface of a lens is coated with a material in which SiO2 and TiO2 are mixed with each other at a ratio of about 5:5 using an IR-coating method. Accordingly, a typical camera module is inappropriate for a biometric authentication device which performs vein authentication by capturing an image using infrared light.
Due thereto, an infrared camera module must be used, but a burden on the manufacturing cost of an authentication device greatly increases because the infrared camera module is expensive.
In order to solve this problem, a conventional biometric authentication device uses a camera module having no infrared blocking function, but further includes an infrared blocking filter and a visible light blocking filter so as to perform both normal imaging and infrared imaging, and then performs normal imaging and infrared imaging for vein authentication in such a way as to alternately switch the filters.
However, such a filter switching-type conventional biometric authentication device is problematic in that, since an internal space, used to individually install the infrared blocking filter and the visible light blocking filter, is required, it is difficult to realize the small size and slim shape of the entire construction.
Furthermore, such a filter switching-type conventional authentication device is considerably inconvenient to use because the infrared blocking filter and the visible light blocking filter block infrared light and visible light, respectively, using a filter switching method. Due to this inconvenience, an automatic scheme is proposed, but this is disadvantageous in that a driving device must be separately installed, thus making it more difficult to realize the small size and slim shape of a device.